On an ordinary morning, J.K. Simmons contemplates the "what ifs" in his life.

The actor, 63, has played dozens of characters over the course of a decades-long career, including a neo-Nazi in the HBO series "Oz," an enigmatic music teacher in "Whiplash" and the guy who knows a thing or two in those Farmers Insurance commercials.

But would those roles, and his other achievements, still have fallen into place if, at roughly 35 years old, a gig as an understudy on Broadway had gone differently?

"I thought I was going to have the opportunity to move up from being the understudy to playing the part," Simmons explains, careful not to reveal the name of the play. "And it seemed like, in a fair world, that would have been the case. The playwright wanted me, the director. It was a perfect match."

"But," he continued, "it didn’t go my way because the producers felt they needed somebody recognizable. It was crushing to me at the time . and I felt ignorantly confident that it was going to happen, because it should have happened."

Simmons went to his agent’s office the next day because he wanted "something else, anything else." That turned out to be the role of Captain Hook in the 1991 Broadway revival of "Peter Pan," where he met his wife, Michelle Schumaker.

"So what seemed like a bad piece of luck professionally led me to my wife," Simmons says. "And here, talking to you. It is interesting to think of what path my career would have taken had that understudy job turned into something. Would I have found my way to ’Whiplash’ or this? I don’t know."

"This" is new spy thriller "Counterpart." Simmons plays two versions of the same character. The Berlin-set series, which continues Sunday on Starz, concerns a bureaucratic agency con-cealing a secret portal to an alternate universe, in which replicas of people diverge slightly from their doppelgangers.

The Times spoke with Simmons about working for two, life after winning an Oscar and his path to acting. The following is an edited version of the conversation.

Los Angeles Times: You said you were surprised by the twist in the series -- had you not been told you’d be playing two characters?Simmons: I don’t know if this is usual or unusual, but whenever my agent sends me something, I just read the script. I don’t read the breakdown because I don’t want my opinion colored by anything other than the script. So, I’m reading the script ... and when ... the Big Reveal happens -- I would love to see video of my reaction because I had a very visceral, physical reaction. It was really mind-blowing. Unfortunately, of course, audiences won’t have that same experience as me because the description of the show is out there.

What kind of scripts had been coming your way after winning an Oscar for "Whiplash"? Had you been looking to return to TV?
No. I was getting a fair amount of (scripts) -- because of Hollywood’s usual lack of imagination -- "Oh, we need a guy who berates everybody in his path. Let’s hire that guy."
But this came along and it wasn’t attached to Starz. I went to the meeting because I loved the script. I did not think I was going to do the job because I wasn’t sure I was right for it. I wasn’t sure I wanted to put in that much time, frankly, because it was clear that it was going to be long hours to play those two characters. Also at the time, the plan was to shoot the whole thing in Europe, and I didn’t want to be away from my family . I said, "I just can’t go off to Europe for 5 months." I have kids in school -- a life that I’m not willing to put on the back burner. Glances were exchanged and, next thing you know, we’re shooting in L.A. I guess you win a few trophies and all of a sudden you can throw your weight around.

What went into forming the identities of what is essentially two versions of the same character?
(Creator and executive producer) Justin Marks and I talked about making distinct physical differences. And in a way, I would have liked to have done it.
I thought, "Well, the first Howard that we meet" -- the kinder, gentler Howard, as I refer to him, and who I really still think of as the protagonist -- "Well, his exercise regime would be riding his bicycle to work and being very cardio, and the other Howard would be in the gym pounding weights." And they would have a slightly different physique. I even went so far as to think, "Is one of these guys vain enough to be wearing a toupee?" And I thought they’ve had different dentists for 30 years, so does one of them have a better set of teeth? But at the end of the day, it was just impractical and expensive.

Keeping the ’what if’ theme going, what do you think you’d be doing if you weren’t acting?
I would probably be a starving musician. When I was in college, studying music, I planned on getting my music education degree as well, but then I did my student teaching, and I realized that: A) I was terrible at it, and B) I really hated it.
As you go along in your education, you realize some teachers are passionate and some are not, and I did not want to be one of those teachers who’s just punching the clock.

Looking at your IMDb page, it’s a stunning list of credits.
It is kind of crazy. I never really had great ambition or a plan. I just fell in love with pretending to be other people. I’ve been fortunate to have enough of a variety offered to me. The reality is, I was not hurting for opportunities before "Whiplash." But since all the attention from that movie, the number of scripts coming my way has increased a lot, but the end result is that I’m working less.